Azalea lace bugs hatch earlier at warmer sites

Azaleas planted next to HVAC equipment that blow hot air. The azaleas always get lace bugs first and worst. Photo: SD Frank

Azalea lace bugs (Stephanitis pyrioides) are one of the most damaging pest of evergreen azaleas. They overwinter as eggs in azalea leaves and begin hatching around now. I found the very first ones yesterday. I found them near HVAC units that blow hot air behind our administration building. This is my monitoring spot for azalea lace bugs because they always hatch here first. In addition the high temperature always leads to greater abundance and damage too.

The first lace bugs of the year. Photo: SD Frank

This is a great example of how high temperature increases advances pest phenology and increases development rate leading to more generations per year. It is also partly why azaleas planted in full sun have so many more lace bugs than those in the shade (where they belong). In shaded places on campus and in my yard I rarely find lace bugs. You can see our research on how urban warming affects scale insect abundance here.

You can actually scout for lace bugs any time of year since azaleas keep their leaves. You will see damage from the previous year even in winter and fecal spots on the underside of leaves. Lace bugs overwinter as eggs so if they were there last year they left eggs waiting to hatch this year. Monitor these plants just by flipping leaves to look for tiny new nymphs.

Azalea lace bug damage on leaves from last year with new leaves above. Photo: SD Frank

Control is best targeted early in the season when nymphs are present for two reasons. First, nymphs are easier to kill than adults and if you kill nymphs before they mature and lay eggs you have a better chance of clearing up the infestation. Second, the longer azalea lace bugs are on your plant the more damage they do. On evergreen azaleas this damage sticks around for a long time so plants may be permanently damaged. So scout your azaleas and get those lace bugs cleared up before damage occurs. Again though the best tactic is not to plant azaleas in full sun (or next to HVAC units) where is is too warm and where natural enemies like green lacewings, spiders, and minute pirate bugs are rare.